Project Summary The Observational Health Data Sciences and Informatics (or OHDSI, pronounced Odyssey) program is a multi-stakeholder, interdisciplinary collaborative formed to bring out the value of health data through large- scale analytics. All our solutions are open-source. OHDSI has established an international network of researchers and observational health databases with a central coordinating center housed at Columbia University?s Department of Biomedical Informatics. Despite the growth of the OHDSI program and related research, many potential stakeholders are unaware of the OHDSI collaborative or how the open-source analytic tools the OHDSI community has developed could support their own research and decision making. To engage with a broader audience, we propose holding a symposium with the objective of raising awareness for OHDSI, and offering hands-on training for OHDSI methods and tools. Furthermore, the symposium will provide a forum to discuss challenges facing large-scale observational research with a broad range of stakeholders, and request external feedback on how OHDSI collaboration could further foster an ecosystem designed to satisfy the needs of the healthcare community. This symposium will be a continuation of our annual symposia offered in 2015, 2016 and 2017. The annual event is open to all stakeholders, from patients to clinicians and researchers to industry and government representatives. At the event, OHDSI collaborators will present OHDSI?s vision and demonstrate our commitment to open science by sharing results from our collaborative studies, carried out across our international research community. Presentations will be interactive and provide participants tangible examples of how observational data has been used to generate real world evidence about disease natural history and the effects of medical interventions. The symposium will give participants an opportunity to provide input on the priorities and future direction for how the OHDSI community should advance the research, development, and applications of observational research. This input will ensure the evidence generated within the OHDSI community is designed to answer the questions most important to patients, payers, providers and policy makers.